Thin films of silicon dioxide and carbon doped silicon oxide are common dielectrics used in fabrication of semiconductor devices. Deposition of the thin films of these materials at low temperatures is typically achieved with Plasma Enhanced Chemical Vapor Deposition (PECVD) process. However, due to concern over potential plasma damage to transistors, a low temperature process is preferred in some circumstances.
Thermal silicon nitrides or silicon carbonitrides have been used as dielectrics, passivation coating, barrier coating, spacers, liners or stressors in semiconductor devices. Limited by tight thermal budget and heat sensitive components in devices, the semiconductor fabrication industry are looking for new precursors allowing deposition of these films at decreasing temperatures. It is projected that the film deposition temperature could be as low as 400 to 450° C. at 22 nm tech node when the mass production starts. To allow the films to be deposited at such a low temperature, the precursors need to decompose at nearly 200° C. and, meanwhile, still meet the requirement for shelf stability. Perhaps the only silane precursors that have been demonstrated thus far to have such a low thermal decomposition temperature and a good shelf life are the hydrazinosilanes developed by Air Products. It has been disclosed that bis(1,1-dimethylhydrazino)ethylsilane, HEtSi(NH-NMe2)2, gives 15 Å/min film growth rate at 370° C. in ammonia. The 1,1-dimethylhydrazino ligand containing a weak N—N bond is known to decompose below 200° C. on a silicon surface. However, the silicon carbonitride films deposited from hydrazinosilanes had the problem of low density.
Bisaminosilacyclobutanes are proposed as a new family of precursors for low temperature deposition of silicon containing films. These molecules have a strained four-membered silacyclobutane ring which may decompose at a low temperature. However because bisaminosilacyclobutanes decompose through different mechanisms than hydrazinosilanes, bisaminosilacyclobutanes are expected to give superior thin film properties. Bisaminosilacyclobutanes have been prepared in 99+% purity, and found to decompose at 200 to 250° C.